Ensure all exceptions have debug_template_source.
Ensure all exceptions have debug_template_source.

Refs #40. Django is not setting debug_template_source attribute on
all TemplateSyntaxErrors (which may be a bug in Django). The
ExceptionReporter assumes it is set, though, so we need to ensure
it is set to something any time we are setting the form's exc_info.

caktus/django-scribbler,imposeren/django-scribbler,caktus/django-scribbler,caktus/django-scribbler,imposeren/django-scribbler,imposeren/django-scribbler,imposeren/django-scribbler,caktus/django-scribbler